Stabilization of chlorinated hydrocarbons



United States Patent O STABHJZATION F CHLORINATED HYDROCARBONS Harry B. Copelin, Niagara Falls, N. Y., assignor to E. I. du Pont de Nemours and Company, Wilmington, DeL, a corporation of Delaware No Drawing. Application May 13, 1954, Serial No. 429,675

11 (Claims. (Cl. Mill-6525) BACKGROUND OF THE INVENTION Chlorinated hydrocarbons today find many uses in industry. Tric-hlorethylene and perchlorethylene, for example, are particularly valuable for accomplishing the vapor degreasing of metals. These compounds are somewhat unstable, however, and undergo reactions with air and the metals they contact yielding products such as hydrogen chloride which seriously impair their utility.

' Heretofore small quantities of addition agents have been added to stabilize the chlorinated hydrocarbons or to new tralize the products formed. Particularly valuable as addition agents are antacids such as the basic amines, commonly used to maintain alkaline conditions in the chlorinated hydrocarbon.

The present invention is concerned primarily with addition agents serving as antacids. Generation of hydrogen chloride and concomitant acidification of the chlorinated hydrocarbons constitutes one of the major problems when these materials are employed, particularly in vapor degreasing. Hydrogen chloride may result from air oxidation of the hydrocarbon or from the decomposition of the chlorinated cutting oils frequently removed from metallic work-pieces by degreasing. When present in even small quantities, hydrogen chloride corrodes the degreaser and catalyzes the rusting of iron or steel workpieces put through the machine. When metallic aluminum is treated in the presence of the acid, aluminum chloride will generally be formed. This salt is a catalyst for the decomposition of the solvent and may be so efiective that the unit must be shut down and the solvent neutralized.

As noted above, amines, such as pyridine, are frequently added to the solvent as antacids since theycombine with free acid and tend to maintain a high pH in the solvent. U. S. P. 2,096,735, among others, discloses the utility of these compounds as acid acceptors. This patent teaches that in vapor degreasing operations employing trichlorethylene or perchlorethylene as solvents,

a basic amine which is suitable for neutralizing acid (HCl) and maintaining an alkaline condition is soluble in the solvent, will react with HCl to form the hydrochloride and whose boiling point is sufficiently close to that of the solvent to insure vaporization of the amine concurrently with the boiling of the solvent, whereby the amine is effective as an antacid both in the liquid and vapor phases. This patent shows that around 0.25% by weight of amine may be used but, in addition, that much higher amounts, i. e. up to 5%, are also acceptable.

2,797,250 Patented June 25, 1957 In practice the quantity employed is limited both by economic considerations and by the fact that a high amine content adversely affects the zinc coatings used in many degreasers. An excess of amine may, furthermore, etch aluminum, remove hydrogen chloride from the solvent molecules and, because of its toxicity, raise a serious ,health problem. As a consequence, the quantity of amine which may be employed is frequently too limited to absorb the hydrogen chloride produced. This situation particularly arises when aluminum chips or fines are present in the degreasers.

OBJECTS OF THE INVENTION ride therein.

GENERAL STATEMENT OF INVENTION The above-mentioned and still further objects may be achieved in accordance with the principles of this invention by supplying a synergist to a chlorinated hydrocarbon containing an amine. Effective synergists for such usage are the organic oxides termed epoxides. These compounds cooperate with the amine to impart thereto a marked increase in eifectiveness as an acid acceptor. Since the epoxide itself is a relatively poor acid acceptor y when utilized alone, its performance when used in combination with the amine is particularly surprising.

The epoxides of this invention are in general organic oxides having the configuration:

The preferred compounds are those having relatively short aliphatic carbon chains, e. g. up to about eight carbon atoms in length. Suitable expoxides include propylene oxide, hutylene oxide, amylene oxide, cyclohexene oxide and others. Halogen substituents in the carbon chain are perfectly acceptable, epichlorohydrin or chloropropylene oxide, for example, yielding excellent results.

The quantity of epoxide employed for synergistic results with an amine is still small but is generally at least about live or ten times the weight of the amine and may be much greater. Usually 0.01-0.5% by weight of the epoxide is suitable but up to 5% may be used if desired. It may be noted that these compounds, although not as effective in neutralizing acids as the amine, do not exhibit the undesirable properties of the latter listed above and unnecessary to use more than 0.1O.2% of the amine.

3 EXAMPLES The invention may be understood in more detail from the following examples, in which all percentages are by weight unless otherwise noted. Each pH given was deter-mined from an aqueous extract of the sampleooncern'ed; Data on aqueous extracts recorded within a given example were taken on samples of equal volume.

Example 1 pH of Initial Sample Sample Additive pH of at End p Sample of Seven Days 0.001% Triethylamine ca. 9. 2 8. 5 0.2% Butylene oxide ca. 7. 3.3 0.02111? Triethylamine+0.2% Butylene ca. 9. 2 9. 1

Example 2 Thisexample shows the effect of a synergistic butyleneoxide-triethylamine combination additive upon a refluxed chlorinated hydrocarbon.

Samples of trichlorethylene were made up and refluxed for 24 hours at ambient pressure. The samples were then extracted with water and the pH of the extracts obtained. The composition of the samples and the results obtained are given in Table II.

TABLE IL-EFFEOT OF SYNERGISTIO BUTYLENE OXIDE- ADDrrrvEs ON REFLUXED TRIOHLORETHYLENE pH at End Sample Additive of 24 Hours Reflux 0.001% Triethylamine 4. 2

0.2% Butylene oxide 2.1

0.001% 'Iriethylamine+0.2 Butylene oxide. 6. 8

The initial pil s of the samples were the same as for the corresponding samples of Example 1.

It will be noted that while the samples containing single additives had become noticeably acidic at the end of 24 hours reflux, that containing two in combination remained close to neutrality. A marked synergistic effect is thus obtained under reflux conditions.

Example 3 This example afiords another illustration of synergism between triethylamine and butylene oxide.

Samples were made up with the same ingredients as the samples of Example 2 and refluxed for 425 hours. Results are shown in Table III.

TABLE IIL-REFLUX OF TRIETHYLAMlNE-BUTYLENE OXIDE SAMPLES FOR 425 HOURS Sample Additive Initial Final 'plEi pH 7 0. 1% Triethylamine... 10. 3.0 0.4% Butylene oxide.-- 7.0 4. 5 0.05%,1Triethylamine+0.2% Butylene 10.2 10.0

4 Example 4 This example shows synergism between triethylamine and cyclohexene oxide.

Samples of trichlorethylene were made up and refluxed for 200 hours. Composition of the samples and results are shown in Table IV.

TABLE IV.REFLUX OF TRIETHYLAMINE-CYOLOHEX- ENE OXIDE SAMPLES FOR 200 HOURS Sample Additive Initial Final pH pH 10 0.02% Triethylamine 10.0 3.9 0.25% Cyclohexene oxide 7. 0 1. 6 0.01% Triethy1amine+0.12% Oyclo- 9.8 9.3

hexene oxide.

Example 5 This example shows the effect of the synergistic additive upon refluxed trichlorethylene samples containing iron powder, i. e. under condit ons simulating those found in degreasers for ferrous materials.

Three samples were made up each containing 300 g. of trichlorethylene and l g. of iron powder. In each sample was placed an additive and the samples were then refluxed. At the end of 16 hours and again after 32 hours the samples were extracted with equal volumes of water and the pH of the water extracts measured. The additives and pHs are shown in Table V.

TABLE V.-EFFEOT OF ADDITIVES ON SAMPLES 0F TRIOHLO BETHYLENE CONTAINING IRON Sample Additive pH-16Hrs. pH-32Hrs. Reflux Reflux .03 g. Triethylamine 4. 6 3. 6 .6 g. Butylene oxide 1.8 1. 7 0.03 g. Triethy1amine+0.6 g. Buty- 8.6 7.0

lene oxide.

It will be seen that the combination of additives remained efiective after 32 hours reflux.

Example 6 This example shows the effect of an additive composed of fl-picoline and epichlorhydri'n.

Aseries of three samples of trichlorethylene was protected respectively by fi-picoline, epichlorhydrin (chloropropylene axide) and a synergistic combination of the two. The samples were refluxed and extracted with water, as in previous tests, at the end of 24 and 48 hours. Table VI shows the results obtained with these runs.

TABLE VI.-.EFFECT OF fl-PIOOLINE AND EPIOHLOBHYDRIN-ADDITIVES Sample Additive pH-24 Hrs. pH-48Hrs.

Reflux Reflux 16---... 0.1% fl-picoline 7. o s. 5

17 0.5% Epichlorhydrin 3. 5 18 0.1% fl-picoline-i-0.6% Epichlorhy- 8.1 7. 7

a m. 1 Not tested. Too acidic after 24 hours to be of value.

Example 7 This example shows the eifect of a synergistic additive, compounded in accordance with the principles of this invention, used in the presence of a cutting oil of a type that may be present in a degreaser.

A series of runs was made with 300 g. samples of trichlorethylene containingBO g. Clorafin 40 cutting oil and pyridine and epichlorhydrin additives separately and combined. The samples are refluxed for 24 hours. Results are tabulated in Table VII.

Tania: vn nrFEoT or 'iymma AND medium DRIN ADDITIVES CUTTING on. MIXTURES TABLE x.-RErLUx or nnso r'aoryminnn xnfl he.

TYLENE OXIDE FOR 50 nouns Sample Additive ix-aims. Sample Additive Initial Final -Reflux PH PH 0.3 g. Pyridine 5. 6 31 0.01% Diisopropylaminai 9. 6 4. 5 0.6 g. Epichlorhydrin 2. 6 32 0.2% Butylene oxide v 7.0 4. 5 0.3 g. Pyridine+0.6 g. Epichlorhydrin 7.0 33 0.005% Diisopropylamine 0.1%

Butylene oxide 9. 2 7. 0

'. 4 l I I V i w I The term cutting oils found throughout this specifi- CONCLUSION cation refers to oily liquids used in metal working to lubricate the metal work-piece. Trichlorethylene is widely employed to remove the cutting oil when a metallic working step is concluded. Clorafin 40 is a proprietary name for a chlorinated oil suitable as a cutting oil.

Example 8 This is a substantial repetition of Example 7.

A series of samples was made up, each consisting of 250 g. trichlorethylene and 100 g. Clorafin 40 oil. To different samples were added different additives and the mixtures then refluxed for 24 hours. Results are shown in Table VIII.

TABLE VIIL-EFFECT OF ADDITIONAL SYNERGISTIO ADDITIVES ON CUTTING OIL MIXTURES Sample Additive pH-24Hrs.

None 3. 9

0.2% Butylene oxide- 3. 9

0.2% Butylene oxide+ Aniline 5.0

- 0.01% Pyridine 5. 2

0.2% Butylene oxide+0.01%Pyridine 6. 2

Run 25 clearly shows the synergism obtained by combining the additives of runs 23 and 24 while run 27 shows that obtained by combining the additives of runs 23 and 26.

Example 9 This example shows the effects of diisopropylamine and cyclohexene oxide additives.

Trichlorethylene samples were made up containing diisopropylamine, cyclohexene oxide and a mixture of these two compounds respectively. The samples were then refluxed as in preceding runs. Results are set forth in Table IX.

TABLE IX.-EFFEOT OF DIISOPROPYLAMINE AND OY- CLOHEXENE OXIDE ADDITIVES Sam 1e Additive pH-200 pH-300 p Hrs. Hrs.

0.003% Diisopropylamine 7. 5 6. 3 0.2% Cyclohexene oxide l 2.0 0.003% Diisopropylamine Oyclohexene oxide 9. 8 0. 8

l Reflux of the sample containing the oxide alone was actually discontinued at the end of 120 hours.

Example The data of the foregoing examples, as for instance as set forth in Table IX, clearly show: (1) that extremely small quantities of amine are efiective antacids when employed synergistically with an epoxide and (2) that the ratio of epoxide to amine in such synergistic antacid pairs may be very large. The epoxidezamine ratio in sample 30 is, for instance, :1 but may be even larger if desired. A possible explanation for these results lies in the cyclic process represented by the following partial equations:

1 Amine+ HClamine HCl and (2) Amine HCl+ epoxide-e Chlorohydrin+amine In efiect neutral epoxide usable in large quantities is consumed while the toxic and expensive amine is constantly regenerated.

It may be noted that the amine-epoxide synergism of this invention is not appreciably affected by certain other additives included in the trichlorethylene. Thus, for example, N-methyl pyrrole and ethyl acetate, known preservatives for chlorinated hydrocarbons, can be included along with an amine and an epoxide in a single sample of the solvent.

Other variations in the exemplified aspects of this invention can be made without departing from the spirit thereof. More than one amine can, for example, be used in the same sample of chlorinated hydrocarbon together with a single oxide. Alternatively, two oxides can be combined with one amine or even with two or more amines. Since no particular advantage accrues from such complex combinations, they are not preferred.

Having now described my invention, I claim:

1. The method of stabilizing trichlorethylene against the formation of acidic products therein which comprises supplying thereto about 0.001-0.2% by weight of a first additive from the group consisting of triethylamine, flpicoline, diisopropylamine, pyridine and aniline and a second additive, synergistically cooperative with the first, from the group consisting of butylene oxide, epochlorhydrin and cyclohexene oxide.

2. The method of claim 1 in which the amine is triethylamine and the epoxide is butylene oxide.

3. The method of claim 1 in which the first additive is triethylamine and the second additive is epichlorhydrin.

4. A composition of matter comprising a chlorinated hydrocarbon degreasing solvent containing about 0.001 to 0.2% by weight of a basic amine which (1) is soluble in said solvent, (2) volatilizes with the solvent when the latter boils and (3) reacts with HCl to form a salt thereof and further contains in solution in said solvent an epoxide capable of reacting with the hydrochloride of said amine to form a chlorohydn'n.

5. The composition of claim 4 in which the basic amine is present in amount equivalent to 0.001 to 0.2% by weight of the chlorinated hydrocarbon degreasing solvent and the epoxide in amount equivalent to 0.01 to 5% by weight of said solvent.

6. A composition of matter comprising a chlorinated hydrocarbon degreasing solvent carrying about 0.001- 0.2% by weight of a first additive from the group consisting of triethylamine, fl-picoline, diisopropylamine, pyridine and aniline and about 0.01-5% by weight of a second additive from the group consisting of butylene 10. The, composition of claim 6 in whichthe chlorinated hydrocarbon degreasing; solvent is'perehlore hylene.

1 1'. The composition of claim 10 in which the first additive is diisopropylamine and the second additive, is cyclohexene oxide.

References Cited in the file of this patent V UNITED STATES PATENTS Missbach Sept. 28, 1937 2,364,588 Morriset a1. Dec. 5, 1944 2,371,644 Petering et a1 Mar. 20, 194 

4. A COMPOSITION OF MATTER COMPRISING A CHLORINATED HYDROCARBON DEGREASING SOLVENT CONTAINING ABOUT 0.001 RO 0.2% BY WEIGHT OF A BASIC AMINE WHICH (1) IN SOLUBLE IN SAID SOLVENT, (I) VOLATILIZED WITH THE SOLVEN WHEN THE LATTER BOILS AND (3) REACTS WITH HCI TO FORM A SALT THEREOF AND FURTHER CONTAINS IN SOLUTION IN SAID SOLVENT AN EPOXIDE CAPABLE OF REACTING WITH THE HYDROCHLORIDE OF SAID AMINE TO FORM A CHLOROHYDRIN. 